CENTAURUS A

'Centaurus A' (also known as '''NGC 5128''') is a lenticular galaxy about 14 million light-years away in the constellation Centaurus. It is one of the closest radio galaxies to Earth, so its active galactic nucleus has been extensively studied by professional astronomers^[1]. The galaxy is also the fifth brightest in the sky, making it an ideal amateur astronomy target^[2], although the galaxy is only visible from low northern latitudes and the southern hemisphere.
A relativistic jet which extracts energy from the vicinity of what is believed to be a supermassive black hole at the center of the galaxy is responsible for emissions in the X-ray and radio wavelengths. By taking radio observations of the jet separated by a decade, astronomers have determined that the inner parts of the jet are moving at about one half of the speed of light. X-rays are produced farther out as the jet collides with surrounding gases resulting in the creation of highly energetic particles.
As observed in other starburst galaxies, a collision is responsible for the intense burst of star formation. Using the Spitzer Space Telescope scientists confirm that Centaurus A is going through a galaxy collision by devouring a spiral galaxy.

Contents

Morphology

Supernovae

Nearby galaxies and galaxy group information

Amateur astronomy information

Other images

See also

External links

References

Morphology

A Hubble Space Telescope (HST) image of the dust disk in front of the nucleus of Centaurus A. Credit: HST/NASA/ESA.

Centaurus A may be described as having a peculiar morphology. As seen from Earth, the galaxy looks like a lenticular or elliptical galaxy with a superimposed dust lane^[3]. The peculiarity of this galaxy was first identified in 1847 by John Herschel, and the galaxy was included in the '''Atlas of Peculiar Galaxies''' (published in 1966) as one of the best examples of a "disturbed" galaxy with dust absorption^[4]. The galaxy's strange morphology is generally recognized as the result of a merger between two smaller galaxies^[5].
The bulge of this galaxy is comprised mainly of evolved red stars³. The dusty disk, however, has been the site of more recent star formation; over 100 star formation regions have been identified in the disk^[6].

Supernovae

One supernova has been detected in Centaurus A^[7]. The supernova, named SN 1986G, was discovered within the dark dust lane of Centaurus A by R. Evans in 1986^[8]. The supernovae was later identified as a type IA supernova^[9]. A type Ia supernova forms when a white dwarf's mass supersedes the maximum mass where it can support itself gravitationally, as may happen when a white dwarf in a binary star system strips gas away from the other star in the system. The white dwarf then collapses, the collapse triggers runaway fusion processes throughout the star, and the star explodes. SN 1986G was used to demonstrate that the spectra of type Ia supernovae are not all identical and that type Ia supernovae may differ in the way that they change in brightness over time⁹.

Nearby galaxies and galaxy group information

Centaurus A is at the center of one of two subgroups within the Centaurus A/M83 Group, a nearby group of galaxies^[10]. Messier 83 (the Southern Pinwheel Galaxy) is at the center of the other subgroup. These two groups are sometimes identified as one group^[11][12] and sometimes identified as two groups^[13]. However, the galaxies around Centaurus A and the galaxies around M83 are physically close to each other, and both subgroups appear not to be moving relative to each other^[14].

Amateur astronomy information

Centaurus A is located approximately 4° north of Omega Centauri (a globular cluster visible with the naked eye). Because the galaxy has a high surface brightness and relatively large angular size, it is an ideal target for amateur astronomy observations. The bright central bulge and dark dust lane are visible even in finderscopes and large binoculars, and additional structure may be seen in larger telescopes.

Other images

See also

★ Messier 87 - ''a giant elliptical galaxy that is also a strong radio source''

★ NGC 1316 - ''a similar lenticular galaxy that is also a strong radio source''

External links

★ 'SEDS': Peculiar Galaxy NGC 5128

★ ESA/Hubble images of Centaurus A

★ 'NASA's APOD': The Galaxy Within Centaurus A (3/4/06)

★ 'NASA's APOD': X-Rays from an Active Galaxy (7/5/03)

★ High-resolution image of Centaurus A showing the discrete elements of galactic core

★ Centaurus A at UniverseToday.com

References

★ STScI. Hubble Provides Multiple Views of How to Feed a Black Hole. Press release: ''Space Telescope Science Institute''. March 14, 1998.

★ Chandra X-Ray Observatory Photo Album Centaurus A Jet
1. Centaurus A - NGC 5128, F. P. Israel, , , Astronomy and Astrophysics Review, 1998
2. The Universe from Your Backyard, D. J. Eicher, , , Cambridge University Press, 1988, ISBN 0-521-36299-7
3. Carnegie Atlas of Galaxies, A. Sandage, J. Bedke, , , Carnegie Institution of Washington, 1994, ISBN 0-87279-667-1
4. Atlas of Peculiar Galaxies, H. Arp, , , Astrophysical Journal Supplement, 1966
5. On the Indentification of Radio Sources, W. Baade, R. Minkowski, , , Astrophysical Journal, 1954
6. An atlas of H II regions in 125 galaxies, P. W. Hodge, R. C. Kennicutt Jr., , , Astrophysical Journal, 1982
7. NASA/IPAC Extragalactic Database
8. Supernova 1986G in NGC 5128, R. Evans, R. H. McNaught, C. Humphries, , , IAU Circular, 1986
9. The type 1a supernova 1986G in NGC 5128 - Optical photometry and spectra, M. M. Phillips, A. C. Phillips, S. R. Heathcote, V. M. Blanco, D. Geisler, D. Hamilton, N. B. Suntzeff, F. J. Jablonski, J. E. Steiner, A. P. Cowley, P. Schmidtke, S. Wyckoff, J. B. Hutchings, J. Tonry, M. A. Strauss, J. R. Thorstensen, W. Honey, J. Maza, M. T. Ruiz, A. U. Landolt, A. Uomoto, R. M. Rich, J. E. Grindlay, H. Cohn, H. A. Smith, J. H. Lutz, R. J. Lavery, A. Saha, , , Publications of the Astronomical Society of the Pacific, 1987
10. New distances to galaxies in the Centaurus A group, I. D. Karachentsev, M. E. Sharina, A. E. Dolphin, E. K. Grebel, D. Geisler, P. Guhathakurta, P. W. Hodge, V. E. Karachetseva, A. Sarajedini, P. Seitzer, , , Astronomy and Astrophysics, 2002
11. Nearby Galaxies Catalog, R. B. Tully, , , Cambridge University Press, 1988, ISBN 0-521-35299-1
12. Groups of galaxies within 80 Mpc. II - The catalogue of groups and group members, P. Fouque, E. Gourgoulhon, P. Chamaraux, G. Paturel, , , Astronomy and Astrophysics Supplement, 1992
13. General study of group membership. II - Determination of nearby groups, A. Garcia, , , Astronomy and Astrophysics Supplement, 1993
14. The Local Group and Other Neighboring Galaxy Groups, I. D. Karachentsev, , , Astronomical Journal, 2005